html,body{
  width: 100%;
  height: 100%;
}

.img1{
  width: 100px;
  height: 100px;
  background: url(./img/1.jpg) center no-repeat;
  background-size: 100% 100%;
}

.img2{
  width: 200px;
  height: 200px;
  background: url(./img/2.jpg) center no-repeat;
  background-size: 100% 100%;
}